Effects of stocking density, ration and temperature on growth, survival and metamorphosis of auricularia larvae of the California sea cucumber, Parastichopus californicus

Abstract

The combined effects of stocking density (0.2, 0.5, 1, 2, 4 and 8 inds/ml) and dietary microalgal ration (20,000 and 40,000 cells/ml) and the sole effect of temperature (10, 12, 14, 16, 18 and 22°C) on the specific growth rate (SGR), per cent survival and per cent metamorphosis of auricularia larvae of the California sea cucumber, Parastichopus californicus, were evaluated in two separate experiments.The SGR was not significantly affected by stocking densities in the range of 0.2 to 4 inds/ml, but was significantly reduced at 8 inds/ml. The SGR of larvae fed 20,000 cells/ml was significantly reduced in comparison to those fed 40,000 cells/ ml. Larvae had significantly higher per cent survival and per cent metamorphosis when reared at densities of 0.2 and 0.5 inds/ml compared with those reared at 2-8 inds/ml. Microalgal ration level did not significantly impact survival or metamorphosis. Larvae reared at 16 and 18°C had significantly higher SGRs and per cent metamorphosis than those held at all other temperatures, while per cent survival was highest at 16°C. Based on these results, we recommend rearing auricularia larvae of P. californicus at a stocking density at or below 0.5 inds/ml, a dietary ration of 40,000 cells/ml, and a temperature of 16°C.

Effect of density, temperature and diet on the growth, survival and development of larvae and juveniles ofIsostichopussp.

“…(2011) and Ren et al. (2017), who evaluated different temperatures between 10°C and 24°C in temperate species such as A. japonicas and P. californicus , observed a positive effect on the growth, development and metamorphosis of the larvae when the temperature increased.…”

“…(2010) in A. japonicas larvae and Ren et al. (2017) in Parastichopus californicus larvae, who evaluated a wide range of larval culture densities (from 0.2 to 10 larvae ml −1 ), observing that as the density increased the survival decreased and the larvae experienced a slow growth and development, showing a reduction in the percentage of larvae that metamorphose to doliolaria, which besides having a smaller size, require more time to reach this stage.…”

“…By day 20 of culture, about 70% of the larvae at a density of 1 larvae ml −1 presented well‐developed hyaline spheres, which are indicative of the end of the auricularia stage and the beginning of metamorphosis (Ramofafia et al., 2003; Ren et al., 2017). Therefore, it is plausible to suppose that the sudden decrease in survival in this density from day 20 of culture is a consequence of the beginning of the metamorphic processes that lead to the formation of the doliolaria larva, going via pentactula to juveniles (Figure 2).…”

“…Therefore, it is plausible to suppose that the sudden decrease in survival in this density from day 20 of culture is a consequence of the beginning of the metamorphic processes that lead to the formation of the doliolaria larva, going via pentactula to juveniles (Figure 2). The increase in mortality could be due to stress generated by the changes that the larva undergoes during this period, in which it does not feed and depends exclusively on the lipid reserves stored in the hyaline spheres (Lacalli & West, 2005; Rakaj et al., 2017; Ramofafia et al., 2003; Ren et al., 2017).…”

Controlled spawning and rearing of the sea cucumber, Parastichopus tremulus

“…The life cycle of the closely related Pacific species Parastichopus californicus has on the other hand been thoroughly documented (Cameron & Fankboner, 1986; Cameron & Fankboner, 1989; Ren, Liu, Dong, & Pearce, 2016; Ren, Liu, & Pearce, 2018). This species lives in similar habitat conditions, has been cultured and tried in co‐culture with, for example, fish and bivalves (Ahlgren, 1998; Hannah, Pearce, & Cross, 2013; Paltzat, Pearce, Barnes, & McKinley, 2008; Ren et al, 2018).…”